In general, a forklift is used for transporting a cargo. More particularly, the forklift is loaded with a cargo on a fork, moves, and unloads the cargo to transport the cargo.
In the meantime, the forklift receives power from a power source and operates a hydraulic system, and the hydraulic system generates hydraulic pressure. The forklift is operated by hydraulic pressure or an engine and a motor, or raises up a fork by hydraulic pressure. Further, the fork may be provided in a mast, and the mast may be inclined forward and backward in the forklift. The aforementioned power source may be an internal combustion engine or an electric motor.
On the other hand, a cargo is mounted on a pallet, and the fork of the forklift is fitted into the pallet. When the fork is raised by an operation of the forklift, the cargo is raised, and when the forklift travels, the cargo is transported.
A travelling path, along which the forklift is to travel, may be a flat road or a slope. The slope road may be understood as an uphill road or a downhill road according to a travelling direction of the forklift.
When the forklift travels, the forklift travels in a state where the mast is tilted backward so as to prevent the cargo from falling. The meaning of the tilted backward is that the mast is tilted toward a main body of the forklift. Similarly, the meaning of the forward tilt is that the mast is tilted in a front direction.
In the related art, an operator controls a degree of forward tilt or a degree of backward tilt of the mast by recognizing a travelling path. Accordingly, the operator needs to appropriately control an inclination angle of the mast at an appropriate time at which the forklift enters or exits from a slope.
On the other hand, a cargo is disposed at a front side of the forklift, so that when the forklift travels in the front direction, the travelling path may be invisible by the cargo. Accordingly, there is a problem in that it is difficult to obtain information on the travelling path, that is, it is difficult to secure a view.
Accordingly, in the related art, it is difficult to adjust an inclination angle of the mast of the forklift at an appropriate time, and further, an operator may not know a degree of adjustment of the inclination angle of the mast. Particularly, the appropriate adjustment of the inclination angle of the mast is considerably varied according to a skill level of an operator, and there may be a case where an unskillful operator incorrectly sets an inclination angle of the mast. Further, there may be a case where an operator completely irrelevantly controls an inclination of the mast in an incorrect direction due to an incorrect determination, and in this case, there is a concern in that the cargo may fall.
On the other hand, in a state where an inclination of the mast is incorrectly set, the cargo may move in a backward direction or a forward direction by inertia when a travelling speed of the forklift is decreased or increased. In any case, the movement of the cargo is in an unstable state, thereby being dangerous. Particularly, when the movement direction of the cargo is the forward direction, a falling danger of the cargo is increased. Here, the forward direction means a direction away from a main body of the forklift.
Further, even when the forklift travels in a state where the mast is excessively tilted backward, the cargo may move according to a change in a speed of the forklift, such that it is required that the inclination of the mast is appropriately maintained.
Korean Patent Application Laid-Open No. 10-2012-0069816 (Jun. 29, 2012) describes further background teachings.